DOI: 10.1002/cvde.200606512 Full Paper Thin Films of ZrO 2 for High-k Applications Employing Engineered Alkoxide- and Amide-Based MOCVD Precursors** By Reji Thomas, Raghunandan Bhakta, Andrian Milanov, Anjana Devi,* and Peter Ehrhart* Ultrathin ZrO 2 films were deposited on SiO x /Si in a multiwafer planetary metal-organic (MO)CVD reactor combined with a liquid delivery system. Two different alkoxide-based precursors, [Zr(O i Pr) 2 (tbaoac) 2 ] and [Zr(O t Bu) 2 (tbaoac) 2 ] are com- pared with two amide-based precursors, [Zr(NEt 2 ) 2 (dbml) 2 ] and [Zr(NEtMe) 2 (guanid) 2 ]. Growth rate, surface roughness, density, and crystallization behavior are compared over a wide range of deposition temperatures (400–700 °C). In addition, the influence of the solvents, n-butylacetate, toluene, and hexane, is discussed. The best growth results in terms of low temper- ature deposition rate, surface roughness, film density, and carbon content were obtained for the new [Zr(NEtMe) 2 (guanid) 2 ] precursor. The electrical properties were investigated with metal–insulator–semiconductor (MIS) capacitors. The relative di- electric permittivity was in the range 17–24, depending on the precursor. Compared to standard SiO 2 capacitors of similar equivalent oxide thickness, low leakage currents were obtained. Keywords: High-k dielectrics, Metal–organic precursors, MOCVD, Zirconium oxide 1. Introduction The technological importance of ZrO 2 thin films is due to the widespread use of this material in oxygen ion con- ductorsand sensors, optical coatings, laser mirrors, wear-re- sistant coatings, magnetic recording disks, biomedical and prosthetic coatings. Recently, interest in ultrathin ZrO 2 films has increased due to the need to find a replacement for SiO 2 as a gate oxide material for future sub-micron electronic devices. [1] The thermal stability and wide band- gap (5.65 eV) of this material and its silicates make it a fa- vorite in this field, together with HfO 2 and its silicates. Ad- ditionally, Zr is an inseparable part of many functional perovskites such as Pb(Zr,Ti)O 3 , BaZrO 3 , and the integra- tion of these materials into semiconductor devices is only a matter of time due to the ever-demanding transistor speed and large memory storage needed to keep pace with Moore’s law. [2] Thin films of ZrO 2 have been fabricated using a variety of methods such as sputtering, pulsed laser deposition (PLD), and chemical deposition methods such as MOCVD and atomic layer deposition (ALD). [1] The complex surface to- pography of the CMOS devices, and possible damage to the channel, together with the need for uniformity over the wa- fer area favor CVD techniques. As amorphous films are preferred for gate-oxide applications due to their better electrical uniformity (spatial invariance of electrical proper- ties), the CVD techniques must be applicable at low tem- peratures. As liquid injection MOCVD is the technique of choice for large-scale production it becomes crucial to find a precursor/solvent combination that does not increase the carbon content in the grown film. Although great progress has been achieved in the development of MOCVD and ALD techniques for the deposition of ultrathin films for gate oxide applications, [1] and in recent precursor devel- opment, [3,4] there is a need for further improvements. In this paper we present a comparative study of four novel MOCVD precursors and, additionally, discuss the effect of the solvent on the deposition characteristics of ZrO 2 films. Electrical properties of the MIS structures will be discussed. 2. Results and Discussion 2.1. Precursors and Solvents The synthesis and characterization of the precursors, a) zirconium bis(isopropoxide)-bis(tert-butylacetoacetate), [Zr(O i Pr) 2 (tbaoac) 2 ], b) zirconium bis(tert-butoxide)-bis- (tert-butylacetoacetate) [Zr(O t Bu) 2 (tbaoac) 2 ], [5,6] c) zir- 98 © 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Chem. Vap. Deposition 2007, 13, 98–104 – [*] Prof. A. Devi, Dr. R. Bhakta, A. Milanov Inorganic Materials Chemistry Group Lehrstuhl für Anorganische Chemie II, Ruhr-University Bochum Universitätsstr.150, D-44780, Bochum, (Germany) E-mail: anjana.devi@rub.de Dr. P. Ehrhart, Dr. R. Thomas IFF-Institut für Festkörperforschung and CNI-Center for Nanoelectronic Systems for Information Technology Forschungszentrum Jülich, 52425, Jülich, (Germany) E-mail: p.erhart@hotmail.de [**] The authors acknowledge financial support from the Deutsche Forschungsgemeinschaft (DFG, CVD-SPP-1119, WA- 908/13-3 and DE-790/3-3). Also, we thank W. Krumpen for the XRF analysis, Dr. U. Breuer for the ToF-SIMS, and H. Haselier for the deposition of the Pt electrodes. Last, but not least, we thank Prof. R. A. Fischer and Prof. R. Waser for their continuous support.